The present invention relates to an atomizing apparatus for atomizing liquid such as liquid fuel, water, liquid drug, and recording medium.
Various proposals have hitherto been made in the field of liquid atomizers employing piezoelectric transducers. In one type of the prior art atomizers, as described in U.S. Pat. No. 3,738,574, there is provided a piezoelectric transducer which is secured to a vibrating element in the shape of a cone so that it amplifies the vibration generated by the transducer. Liquid is supplied to a plate attached to the apex of the hone where the vibration is at a maximum.
This prior art atomizing apparatus, however, requires that the vibrating element be manufactured in a close range of tolerance. Further, difficulties have been encountered in supplying the liquid to the vibrating element. A further disadvantage is that it requires a fairly large amount of power, specifically, a power output of 5 to 10 watts is needed to effect the atomization at a rate of 20 cc/min.
In ink jet printers, a typical example of which is described in U.S. Pat. No. 3,747,120, liquid is held in a chamber which is defined at the rearward end by a piezoelectric transducer to produce short duration pressure rises therein, the chamber being in comunication with a nozzle provided at the forward end. The liquid is ejected in the form of a jet at a considerably high speed to a writing surface in response to the short duration pressure rises. Although effective for printing purposes, this type of atomization is not operable with liquid of the type which contains a substantial amount of air such as kerosene since such resolved air tends to cause cavitation as the pressure rise advances through the bulk of the liquid from the rear to the front end of the liquid chamber.
Prior art driving circuits that generate a high frequency continuous wave include an oscillator and an amplifier that applies an amplified continuous wave voltage to the piezoelectric transducer. A typical example of such circuits is shown in FIG. 1 in which the frequency of an oscillator 2 is tuned to the resonant frequency of a piezoelectric transducer 1 to maximize its operating efficiency and applied thereto via an amplifier 3. However, with a change in ambient temperature the resonant frequency of the piezoelectric transducer deviates from the oscillator frequency. To compensate for such deviations a phase detector would be required to detect the difference in phase between the voltage and current of the signal applied to the piezoelectric transducer and provide a feedback signal to the oscillator so that the oscillator frequency closely follows the temperature dependent shift in the resonant frequency. In this case an oscillator of a variable frequency type is required.
Another prior art driving circuit employs a colpitz oscillator circuit as shown in FIG. 2 in which the piezoelectric transducer 1 is connected across the base and collector of a transistor 6 with a capacitor 4 being coupled between the base and emitter of that transistor and another capacitor 5 being coupled across the collector and emitter of the transistor. This circuit utilizes the piezoelectric transducer as an inductive component of the oscillator. Although the oscillator frequency follows the temperature variation, use of this type of oscillators is only limited to piezoelectric transducers having inductive property.